Tetrahydrocannabinol

Nabiximols — a standardised 1:1 THC:CBD oromucosal spray — is licensed in many countries for multiple-sclerosis spasticity that resists first-line drugs. A meta-analysis of the pivotal RCTs found a modest but reproducible reduction in patient-rated spasticity ^{2Reference 2Wade DT et al. · 2010Meta-analysisMeta-analysis of the efficacy and safety of Sativex (nabiximols) on spasticity in people with multiple sclerosisView study →}, and the 2022 Cochrane review rates the evidence low-to-moderate certainty with a small average effect ^{3Reference 3Filippini G et al. · 2022Systematic reviewCannabis and cannabinoids for symptomatic treatment for people with multiple sclerosis — Cochrane systematic reviewView study →}.

Gap: the effect is modest and driven partly by subjective self-report; roughly half of patients are non-responders, and the standardised spray doesn’t represent smoked or edible cannabis ^{3Reference 3Filippini G et al. · 2022Systematic reviewCannabis and cannabinoids for symptomatic treatment for people with multiple sclerosis — Cochrane systematic reviewView study →}.

Synthetic THC (dronabinol, nabilone) has been a licensed antiemetic since the 1980s — one of cannabis’s oldest evidence-based uses. A Cochrane review found cannabinoids more effective than placebo and broadly comparable to older antiemetics, and often the treatment patients preferred ^{1Reference 1Smith LA et al. · 2015Systematic reviewCannabinoids for nausea and vomiting in adults with cancer receiving chemotherapy — Cochrane systematic reviewView study →}.

Gap: the trials predate modern antiemetics; benefit over today’s standard drugs (setrons, NK1 antagonists) is unproven, so THC now sits as an option for nausea that resists first-line therapy ^{1Reference 1Smith LA et al. · 2015Systematic reviewCannabinoids for nausea and vomiting in adults with cancer receiving chemotherapy — Cochrane systematic reviewView study →}.

Across many RCTs and a 2026 Cochrane review, cannabis-based medicines produce a small reduction in chronic neuropathic pain, with sedation and dizziness common ^{6Reference 62026Systematic reviewCannabis-based medicines for chronic neuropathic pain in adults — Cochrane systematic reviewView study →}; the JAMA umbrella review rated the overall pain evidence moderate-quality ^{5Reference 5Whiting PF et al. · 2015Meta-analysisCannabinoids for Medical Use: A Systematic Review and Meta-analysisView study →}. THC is a genuine but modest analgesic, best considered for stubborn nerve pain rather than pain in general.

Gap: effect sizes are small and inconsistent, and in cancer pain specifically the evidence is largely null ^{5,6Reference 5Whiting PF et al. · 2015Meta-analysisCannabinoids for Medical Use: A Systematic Review and Meta-analysisView study →Reference 62026Systematic reviewCannabis-based medicines for chronic neuropathic pain in adults — Cochrane systematic reviewView study →}.

The appetite-stimulating “munchies” effect is real — THC drives appetite through CB1 receptors — and dronabinol supported appetite in HIV-associated wasting. In cancer cachexia, though, controlled trials are largely null: cannabinoids didn’t beat placebo or megestrol for appetite or weight ^{4Reference 4Mücke M et al. · 2018Meta-analysisSystematic review and meta-analysis of cannabinoids in palliative medicineView study →}.

Gap: the appetite effect is pharmacologically genuine but clinically unreliable where it’s most needed ^{4Reference 4Mücke M et al. · 2018Meta-analysisSystematic review and meta-analysis of cannabinoids in palliative medicineView study →}.

A textbook case of a real effect that isn’t useful. THC does lower intraocular pressure, but only for about 3–4 hours per dose, which would demand near-continuous (and continuously intoxicating) dosing — which is why ophthalmology bodies don’t recommend it ^{8Reference 8Tomida I et al. · 2004ReviewCannabinoids and glaucoma — reviewView study →}.

Gap: the pressure-lowering is too short-lived to be practical, and no cannabis preparation is a recommended glaucoma therapy ^{8Reference 8Tomida I et al. · 2004ReviewCannabinoids and glaucoma — reviewView study →}.